Combined cycle power plant with flue gas recirculation

Abstract

An exemplary system method for the operation of a CCP P with flue gas recirculation to reduce NOx emissions and / or to increase the CO2 concentration in the flue gases to facilitate CO2 capture from the flue gases is disclosed. The flue gas recirculation rate (rFRG) is controlled as function of the combustion pressure and / or the hot gas temperature. Operability is enhanced by admixing of oxygen or oxygen enriched air to the gas turbine inlet gases or to the combustion.

Description

RELATED APPLICATIONThis application claims priority under 35 U.S.C. §119 to Swiss Patent Application No. 00841 / 10 filed in Switzerland on May 26, 2010, the entire content of which is hereby incorporated by reference in its entirety.FIELDThe disclosure relates to power plants, such as a method for operating a combined cycle power plant with flue gas recirculation as well as to a plant to carry out such a method.BACKGROUND INFORMATIONIn recent years it has become obvious that the generation of greenhouse gases leads to global warming and that further increase in greenhouse gas production will accelerate global warming. CO2 (carbon dioxide) is identified as a main greenhouse gas and NOx is believed to significantly contribute to the greenhouse effect as an indirect greenhouse gas by producing ozone in the troposphere. CCS (carbon capture and storage) and reduction of NOx emissions are considered potential major means to reduce and to control global warming.Reduction of NOx emissions ca...

AI Technical Summary

Problems solved by technology

Due to the relatively low CO2 concentration of the flue gases of a conventional CCPP, such as 4% for example, the CO2 capture system (also called CO2 capture plant or CO2 capture equipment) for a conventional CCPP can be more costly and energy consuming per kg of captured CO2 than the ones for other types of fossil power plants, such as coal fired plants, which have a relatively higher CO2 concentration.

This variation in the CO2 concentration can be detrimental to the performance, efficiency, and operatability of the CO2 capture system.

However, flue gas recirculation reduces the oxygen content in the inlet gases of the gas turbine and affects combustion.

Besides positive effects on NOx emission the reduced oxygen content can lead to an incomplete unstable combustion and result in high CO emissions, which is highly undesirable.

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